A project to remove invasive algae from Kaneohe Bay has taken 250,000 pounds of algae out of the bay, clearing 20 acres of reefs and replacing the algae with 150,000 native sea urchins, which prevent algae from building up again, according to the Nature Conservancy of Hawaii.

The project has been going on for a year and a half, the Conservancy said, using a barge with a large vacuum known as the Super Sucker.

The state Division of Aquatic Resources has been raising native sea urchins at its Anue­nue Fisheries Research Center and releasing them into the bay to keep the algae from growing back. The state hopes to produce and release more than 200,000 urchins in 2014, the Conservancy said.

The invasive algae removed from the bay is given to local farmers to use as compost.

"Kaneohe Bay provides so much to so many people," says Kim Hum, the conservancy’s Hawaii director of marine conservation. "You look out here and it’s just beautiful. Hundreds of people use the bay every day.

"But I think most people don’t understand what’s going on underneath the bay, that there’s a problem here. The good news is that we know how to fix it, and we just have to continue to work together to do that."